


Damn Hormones and Instincts

by Night-Mare (Aoife)



Category: Katekyou Hitman Reborn!
Genre: Age Difference, Alternate Universe - Canon Divergence, Background Gokudera Hayato/Yamamoto Takeshi, Dubious Consent, M/M, Male Pregnancy, Non-Traditional Alpha/Beta/Omega Dynamics, POV Yamamoto Tsuyoshi, Reborn is a Menace
Language: English
Status: Completed
Published: 2020-03-06
Updated: 2020-03-06
Packaged: 2021-02-26 14:27:08
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,752
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23042434
Author URL: https://archiveofourown.org/users/Aoife/pseuds/Night-Mare
Summary: It's been seventeen years since he last felt these symptoms, but they're unmistakable, the legacy of his Family's two millennia plus of Flame Use. As much as it sucked, he was going to have to ride it out on his own; his Sky had died allowing him and Takeshi to escape an ambush.The only problem with his plan is that Reborn is amenace.
Relationships: Sawada Tsunayoshi/Yamamoto Tsuyoshi
Comments: 2
Kudos: 116





	Damn Hormones and Instincts

“Escape Reborn’s Training with my Dying Will!” He snorts in amusement and lays out his knives, checking the blades of each of them for sharpness and reaching for his whetstone when he finds two have ever so slightly raggedy edges. The little Sky was going to suffer for those words, even if they were totally heartfelt. Reborn wasn’t the kindest tutor anyone could have, especially not the clumsy little ball of fluff in his son’s class at Nami-koko; he’d seen him trip over thin air and run from dogs smaller than the local rats. But the kid’s Flames - when they were forced out, at least - were syrup sweet and tempting, the very personification of a Sky of breeding age. He shoves any temptation into the box in the back of his head and picks up one of the damaged blades and the stone, and he perches on his stool and strokes the blade methodically, working out the nick that would become a problem if he kept using it; Tsunayoshi was his son’s Sky to court, even if his silly boy hadn’t started doing so yet.

(If anyone other than his silly boy was the one circling Tsunayoshi he’d already be creeping closer himself, ready to make an offer to him; he’d had a Sky once upon a time, and the bit of fluff’s Flames were warming the cold dark hole their death had left.)

“I’m going to baseball practice, otousama -” he looks up at his son, methodically checking him over with a practised eye; his son only used that honorific when he was up to something. He still wasn’t showing any signs of being a bearer, and despite his initial promise to take his sword work more seriously, he’d slid back towards baseball.

“You’re going to lose your Sky, musuko -”

“Maa, maa. Tsuna-kun doesn’t want me to give up baseball.” He sighs, and picks up the second blade. The little Sky might not _want_ his son to give up baseball, but the number of men he’d killed in the past six months said he _needed_ him to.

“Be home for dinner, Takeshi-kun; and check on your Sky for me; Reborn’s been shooting at him already this morning.”

“Sure. But he’ll be fine, tousan.” He shakes his head, and his son vanishes out the door, leaving him to return to his blade sharpening; once all of his cooking knives are done, he tucks them back into their roll and pulls the other set out of the Mist his fellow Guardian had wrapped them in for him once upon a time. These need more work; fish bones rarely chipped his blades, but human bones were more substantial and Italian mafioso didn’t like staying still to be killed, and their pistols were hell on his blades.

He spreads his Flames, tapping into the sensory enhancement net that the adorably Cloudy little demon Kasumi insisted was her son had laid over the town to protect his Sky. “If you don’t want to hear that sort of thing, then don’t shoot me when I’m trying to have a private moment, Reborn -” he snickers, picking up his kodachi and starting to work on the blade with slow, steady strokes, coaxing the nick out of the blade with a careful use of his Flames. (The trick was to relax the bonds within the metal just enough to do the repair without weakening it; it had taken him years and many wasted blades to figure it out.)

His Flames ebb and flow, curling in the net, and keeping half an eye on the little bit of fluff masquerading as his son’s Sky until they’re shoved out of it unceremoniously by Kasumi’s demon child as he wakes up and takes over guard duties. (The boy was a nekomata; he was willing to _swear_ it. He certainly had the sleep patterns of a cranky cat yōkai.) That leaves him with his Flames flaring, and he catches the edge of another spike of Sky Flames and they latch onto it instinctively, their syrupy sweet temptation yanking at something deep in his belly with vicious force, leaving him doubled over panting, his cock hard and his body throbbing.

Shit. He wasn’t supposed to feel like this. He wasn’t supposed to feel like this because of his son’s teenage Sky. But he’s been the reproductive focus of a Sky, knows what it feels like for his Flames to make space for a child to settle inside his body, and this is fucking humiliating. He should have more self-control than this, should be an adult, should be above being tempted to yield to the tiny ball of fluff that Reborn was currently terrorising into a candidate for Vongola Decimo.

Except that even if he was a tiny ball of fluff, he was a _powerful_ ball of fluff. Powerful enough to pull anyone in and make them want a child from him; perhaps he’s lucky he’s not competing with his son for the attention of Tsunayoshi’s Flames. Fuck. He shoves back from the table, dismissing his blades - even though some of them still need repair - and heads back upstairs to his bedroom with its sad single futon and slams the door, sealing it behind him. (He does crack the window; he can smell himself, smell his arousal, and his body’s preparations to be bred, and the scent will stick and grow stifling if he doesn’t take precautions.) 

He strips his clothes off; they feel confining all of a sudden, despite the fact he favoured more traditional clothing, and he sighs and folds them, dropping them on top of his clothing chest, and then sprawls on his futon. He runs his fingers over his abdomen, feeling the way it’s already changed, and down to his cock, half-hard against his thigh. Beneath it, his balls are absent and he whines; if he didn’t know what was going on, it’d be a sound of distress, but instead, it’s merely an ‘oh gods, not again’. The slit that’s in their place is wet, but barely open, only half-formed so far, and he rolls over and screams into the pillows. 

Once he’s done venting his rage, he rolls back over and strokes himself with his wet fingers, jacking himself off, savouring the feeling of his own cock; if he did surrender, there would be weeks and months where he wouldn’t be able to touch himself so easily. (Takeshi had certainly gotten in the way of masturbating.) He’s already incredibly sensitive; it’s one of the few benefits of the adjustments his Flames were making to his body. 

“Tsuyoshi-oji -” he yanks the blanket over his body, hissing at the rough fabric, and glowers at the demon child. “- you’re in Heat.”

“Fucking _knock_, brat.”

“I did. Which Sky -?” He flares at him, snarling. “- the small animal?”

“Which other fucking sky, oni-kun?”

“Hn.” He takes that as ‘Point’, and the brat drops away from his window, leaving him in peace to try and get off. The interruption has cooled his ardour though, and he gives up with a frustrated growl, rolling off the futon and heading for the door to the main room - there’s no one there, and he still has the supplies from when this happened before compressed into a Mist ball that he’d shoved in a drawer. Maybe if he fucks himself on something he can get some relief from the maddening itch under his skin?

He retrieves the ball, and opens it when he’s back in his bedroom, revealing a dizzying array of dildos. (He’d run after his Sky’s death, before Takeshi was born, and had needed _something _ to keep himself sane.) He selects a slender one and the base - like a seiza stool, one that he could pin in place with his legs while he could fuck himself - attaching the two parts together and lubricating the post generously. He lines himself up with the dildo, pinning it in place and sits down on it. 

He means to go slowly, to ease himself back into the game, but his body accepts its length so sweetly that he’s firmly planted on it before he even realises. Fuck. He was far further along than he thought he was; he’d not intended to use more than six inches of its length, but instead, his body had swallowed all twelve effortlessly. His cock perks up, of course, the traitorous organ; it’s primed to find the presence of a cock or something close enough for stimulation arousing, and he strokes himself, bouncing gently on the post, and oh, that was better. So much better.

Finding his rhythm; well, it’s like finding the muscle memory for his sword kata. Effortless.

He twists his wrist, slams down onto the stool and cums, and the door creaks open. He shuts his eyes in despair at the warm flood of surprised Sky Flames. He knew he’d forgotten _something_; what the fuck did he look like? He’s impaled on twelve inches of cherrywood, his cock in hand, he visibly has no balls and his Flames are boiling like there’s a typhoon lashing at him.

“Hiiieee! Kyō-nii said you needed me Tsuyoshi-sama?! Something about the carnivore finally going back into heat -” He opens his eyes, and _oh_. Tsunayoshi’s hard. Rock hard. Flames flickering and barely restrained from curling around his. “- Kyō-nii meant you? Why -”

“Baka-Tsunayoshi.” There’s a gunshot, and a ‘hiiieee’ and he sways drunkenly as the full force of the Sky’s Will and Flames focus on him. Tsunayoshi’s an order of magnitude stronger that his former Sky, young and strong and right there while his body needs. The next few minutes are blurry, dizzying, body strung out on aching pleasure as he’s coaxed into presenting himself, his slit open and _dripping_ lube, hungry for the Flames and cock of the Sky in the room with him.

Tsunayoshi’s cock is fat and hot and perfect, sinking into him like a hot knife into butter and it feels like he’s crammed _full_. Too full and just full enough; it fills the slit behind his cock painfully full. Stretches the thin, tight skin to the point where he’s almost terrified of tearing except that he can’t think enough to make that thought coherent. His Sky holds still over him, small hands holding his thighs up and open and Dying Will Flame on his forehead. Once he’s focused on the small Flame in his forehead, his Sky rolls his hips, fucking him with slow, smooth strokes that make his fire burn in a way that the dildo and his own hand hadn’t.

The friction is exquisite. Hot, stark fire that curls up his spine. 

One of his small Sky’s hands drops to his cock, stroking it equally slowly, coaxing him towards another orgasm, one that’ll be mind-bending in its intensity. (He remembers Takeshi’s conception. Remembers how explosive it was. Remembers the moment of vulnerability.) He clenches around the cock in his slit, and Tsunayoshi’s hips stutter, the little Sky’s Flame guttering on his forehead. “You need to cum with me, koneko. If you’re here to breed me, then we need to cum together.” The little Sky whines, gritting his teeth, the Flame brightening in intensity four or fivefold. “I’m really close, I promise. Just stroke the underside of my cockhead with your fingernail, koneko -”

Tsunayoshi complies, and the pleasure coiling in his gut unravels in one spectacular moment that’s accompanied with a flare of Flames and his Sky follows suit so closely that it counts as simultaneous. (The crest of Sky Flames breaks over, tearing through him fast and vicious, searing pleasure that blinds him to everything but being possessed by a Sky that’s an even more perfect match for him than his first, Takeshi’s sire.) 

“Mine.” The one word is choked out, the Flame on Tsunayoshi’s forehead guttering out as he collapses on top of him, his soft cock sliding free of his slit, and he rolls on his side, cuddling the boy close. His new Sky is tiny, his mother’s son through and through; he’s met the Idiot masquerading as his new child’s grandfather, and there’s no sign of the man’s height or ’blond’ness in Tsunayoshi. He curls around him, resting his head in soft brown hair, and tries to think through the ache between his thighs and the intoxication of having the empty part of his soul full again. (That doesn’t even account for the spark of his brand new pregnancy.)

He drifts, the Flames in the room soft and warm and adoring, and he doesn’t know what he’s supposed to do or say, to make this right or to make it all make sense. 

Before he panics though, he settles into his Flames, and stretches his sense through them in the way his first Sky had shown him; he’d been the Cloudiest of their set, and he’d done it to settle his instincts. He brushes against Tsunayoshi’s dull embers, the Seal enclosing much of his Flames still; the wide expanse of Kyō-oni-kun’s Cloud; his son’s Rain. He blinks, dropping back into his bedroom and presses a kiss to his new Sky’s forehead. He’d thought that a single Sky holding multiple Flames at a ‘Guardian’ level was mythological. 

“Hiiieee. I’m sorry Tsuyoshi-sama.”

“What for, little one?”

“I. We. Reborn -”

He makes a small amused sound. “Oh, Tsunayoshi. Reborn’s a menace and, um, you can’t make me regret a sibling for Takeshi; my first Sky promised me as many as I wanted when I presented, but circumstances thwarted us.”

“Hiiieee.” He laughs, rolling onto his back. 

“This has to be the third or fourth strangest thing that has happened to me.” His Sky makes a confused sound. “How I went Flame Active, discovering I could bear and giving birth all top it, just. And finding a new Sky wouldn’t feature at all; it’s just _sharing_ a Sky with my son that’s making it feel so odd, I think. Sixteen years isn’t the biggest gap I’ve seen between a Sky and Guardian either; it’s not the biggest you’ve seen, either. Romario and Dino have almost twenty years between them and two foals.”

“Hiiieee! Dino has children? You’re pregnant now?!”

“Yes to both. Your oniisama keeps his foals well hidden, but they’re eight and six if I remember correctly; little girls.” His Sky squeaks. “And Flame Users aren’t standard human, little one. We can tell immediately.” His Sky is half-hard against him, and he rolls them both so that Tsunayoshi is underneath him, and presses a kiss to his lips. “Given that we may as well be hung for a sheep as for a lamb, -” he rolls his hips, sliding his cock against Tsunayoshi’s; both of them are slick and messy and from experience, he knows the lube he produces is like nothing else. His Sky hiccups and looks up at him with big eyes, hips jerking ever so slightly.

“You want to do it again, Tsuyoshi-sama?”

“Mhmm. You felt very good inside me.” He rocks again, sliding the full length of his cock against his Sky’s; it feels good against his cock but it would feel even better inside him. “I like being fucked, Tsunayoshi. It feels very, very good; part of it is biology, making it rewarding to be penetrated, to be bred, but I genuinely like it even when my slit’s absent. I’ve made do with my hand and a single toy for the last fifteen years, but providing you’re willing I’d rather not go without, at least while I’m pregnant.” 

Tsunayoshi is hard underneath him, hips rocking up into his downward thrusts and he hisses in victory, sliding forward and then back, successfully ‘catching’ himself on his Sky’s cock and stuffing himself full of it all over again. It feels just as good as the first time, and if his balls never drop again, he won’t be sorry. (Mostly, because it’ll mean he’s continued to be enthusiastically ploughed by his Sky.) And Tsunayoshi’s teetering on the edge of taking the Active role even without one of Reborn’s bullets pulling his strings.

“If you’re sure?” He nods and then muffles a squeak as the flame on his Sky’s forehead catches again, and their positions reverse; he’s amused. He didn’t think Tsunayoshi was capable of spontaneous Dying Will Mode, but that was clearly its Flame on his forehead. “Am I - am I doing it right?” He reaches up and ruffles his Sky’s hair, clenching his muscles around the cock buried in his slit.

“Just follow your intuition, koneko. Do what feels good to you; I’ll tell you if it doesn’t work for me.” His Sky squeaks, those orange eyes locked on him and Tsunayoshi shifts, a long slow drag of his cock out of his slit that makes him whine; he’s already getting greedily accustomed to being crammed full of cock again and its absence is going to make him feel needy -

Before he can complain about how empty he is, Tsunayoshi shoves back into him, a raggedy-but-deep stroke that stuffs him so full that he moans in pleasure. It feels amazing, the friction, the stretch and he arches, whining as Tsunayoshi pulls back again, pulls out, then fucks back into him, taking his pleasure, demanding it and he makes pleased, encouraging sounds, coaxing his Sky into being less careful with him. It takes Tsunayoshi time to comply with his demands, but he does and it builds the fire at his core until it’s threatening to consume him whole. A small hand wraps around his cock, stroking it, and that’s more than enough to allow him to reach completion; Tsuna fucks him through it, keeps driving into his slick slit until he’s half-insane with the friction and the muscles around his Sky’s cock jump and twitch and convulse as they’re overstimulated.

“Don’t stop -” his Sky doesn’t, but he does speed up, clearly chasing his own orgasm. His thrusts go ragged, and he encourages his Sky to keep fucking him, keep taking pleasure in his body. He slides into another orgasm, one that’s blinding in its intensity. (Literally blinding; he has to blink spots from his eyes as his Sky collapses on top of him again.) It’s just as well his room is normally almost painfully bare; if it hadn’t been, it would be now. His Sky’s control over his Flames is almost negligible thanks to the Seal - he kicks himself for not having spotted it years ago - and the room had been reduced to just the Flame-hardened elements. 

“Tsuyoshi-sama -”

“You’re okay, Tsuna. And I think after that, we don’t need to use honorifics.”

“Hiiieee.” He laughs and buries his head in the soft brown hair all over again. He stretches his Flames, soothing the flickering, flaring Flames at the centre of his Sky’s being. They calm, and his Sky curls into him like an exhausted little kitten. “But, but -”

“Shhh. Reborn’s done you a shitty turn, Tsuna. He should have explained rather than just throw you in here.” His Sky makes a small disbelieving sound. “Bearer-elements appear at about the same rate as Skies, though there might be two or three in a set; they can conceive with their Sky no matter their apparent genders.” He presses another kiss to his Sky’s forehead. “We know when our body adapts; we end up having something like a cat’s heat. I was preparing to fuck myself through it with toys when Reborn threw you in here.”

“Is Takeshi -”

“Maybe. He’s not showing any real signs of it, but he should be. Sky-bearer relationships tend to produce Skies. Or bearers.” But Tsuna’s question has him reframing his son’s behaviour in terms of a budding bearer; he’d seen flashes of every Flame from Smoking Bomb. There had been rumours about the boy, the behaviour of his father towards his mistress and wife excused because of the possibility they’d finally transitioned to being a Sky-line. “Except he is. But he’s focused on your Right Hand. Gokudera-kun must have a Sky secondary.” His Sky hums against his chest, giggling slightly. “When he showed so strongly Stormy, everyone forgot they thought he was a Sky.”

“Mmhmm. Been teaching Hayato. Using his Sky helps him manage his temper.” His Sky nuzzles against him, rocking his hips slightly, making him aware of the fact he’s still inside him, held in place by his locked-tight muscles. “Would Keshi-kun presenting explain why he’s been stalking Hayato, Tsuyo-sama?”

“Yes.” He swallows. “But we can continue this discussion later, Tsuna. When we’re both dressed and your cock’s softened; right now I need you again -” his Sky squeaks, and stills. He whines, clenching tight muscles tighter, and his Sky responds by resuming movement, his cock dragging achingly slowly against oversensitive flesh. One more round, probably. One more load of rich, Sky-flooded cum inside his womb. Three rounds would take probable to certain, and he should tell his Sky that, but he’s greedy, has always wanted more children, but being a bearer sort of precludes the other route. 

His Sky’s hand drops to the base of his cock and his thumb rubs against it gently, at the hypersensitive point where the base of his cock meets his slit, and he shrieks; he’d known it felt good - did feel good even when his body reverted, and that it was a marker of what he was - but having one of Tsunayoshi’s small fingers rubbing at it, channelling Sky Flames into the small patch took it from enjoyable to agonisingly good. “You like that, Tsuyo-sama?”

“Perfect, Tsuna-koi.” His Sky whines softly, still rubbing at the small patch as he rocks his hips. “Shhh. One more time and the first wave will be done. One more time and we can figure out what to do next.” He clenches again, enjoying the feeling of friction, of the way his body is still eager, even of his cervix being stimulated by his Sky’s cock. (It’s ripe and open and he can feel the weight of the small pouch behind it; it’s sucked up all of his Sky’s fluids and he can feel the spark of possibility cradled in its centre.) He’s so _full_. So very full, Tsuna’s cock perfect and hot and hard inside him and he arches, so close. So very close -

He shrieks and cums, his back arching, his body milking his Sky’s cock with ruthless and vicious need. Tsuna collapses on him, spent, and he hums and blankets them both in Rain Flames, using a touch of his secondary Flame to ensure they’ll stay comfortably warm and then follows his Sky into sleep.


End file.
